Self-contained die cushion



June 2, 1964 J. c. DANLY ETAL 3,135,169

SELFCONTAINED DIE CUSHION Filed June 8, 1961 5 h e 5 Lu I INVENTORS l \TQMES C. DEM/LY 2/6 222 (A BQ/HSIL GEOPGEFF F] TTOENE Y United States Patent 3,135,169 SELF-CONTAINED DIE CUSHION James C. Danly, River Forest, and Vasil Georgelr', La

Grange Park, 111., assignor to Danly Machine Specialties, Inc Chicago, 111., a corporation of Illinois Filed June 8, 1961, Ser. No. 115,734 8 Claims. (Cl. 91-416) Our invention relates to a self-contained die cushion and more particularly to an improved self-contained die cushion which does not require large diameter pipes running to tanks external to the press bed and which obviates the possibility of excessive pressure buildup in the cushion.

In the art of power presses, die cushions including a relatively movable cushion piston and cylinder are employed resiliently to support movable parts of the lower die with which the press operates. Fluid under pressure is supplied to the space between the piston and the cylinder normally to raise the movable die part to an operative position. When in the course of a press operation the working slide of the press moves downwardly, it forces the movable part of the lower die downwardly against the pressure of the fluid such as air in the die cushion.

In press installations in which dies are to be changed or adjusted at relatively frequent intervals, it is desirable that the press cushion be rapidly exhausted to lower the cushion to its inoperative position to permit work to be done on the lower die. It is desirable also that the arrangement permit the cushion to'be moved rapidly to its operative position when the press is again to be conditioned for operation.

It has been suggested in the prior art that the cushion piston be inverted with the open end of the piston facing the open end of the cylinder slidably received by the piston to permit the fluid under pressure to be exhausted rapidly from the space between the cushion piston and cylinder. While this arrangement permits the cushion to be rapidly exhausted, it requires relatively large diameter pipes and large diameter valves leading to tanks external to the press bed if the cushion is to be returned to its operative position rapidly.

We have invented a self-contained die cushion which permits the fluid under pressure to be rapidly exhausted from the space between the cylinder and the piston and which permits the cushion to be rapidly returned to its operative position without at the same time requiring large diameter piping and valves leading to tanks external to the press bed. Our improved self-contained die cushion accomplishes this result without the danger of undue restriction of fluid or the danger of excessive pressure buildup within the cushion.

One object or" our invention is to provide a self-contained die cushion which permits the fluid between the cushion piston and cylinder to be rapidly exhausted while at the same time permitting the cushion to be returned rapidly to operating pressure in its operative position.

Another object of our invention is to provide a selfcontained die cushion which can rapidly be stroked without requiring large diameter pipes and valves for connecting the cushion to a tank external to the press bed.

Still another object of our invention is to provide a self-contained die cushion in which we maintain a reservoir of fluid under the cushion operating pressure when the cushion has been lowered to its inoperative position.

A further object of our invention is to provide a selfcontained die cushion which fails safe in that the cushion will return to an inoperative position in the event of either a loss of fluid pressure or an electrical power failure.

' A still further object of our invention is to provide a self-contained die cushion which may rapidly be stroked without the danger of undue restriction to the flow of fluid or the danger of excessive pressure buildup.

Other and further objects of our invention will appear from the following description.

In general our invention contemplates the provision of a self-contained die cushion comprising a piston and cylinder mounted for relative movement together with a control valve built into the piston for controlling the flow of fluid from within the hollow piston to the space between the piston and cylinder. We provide our cushion with an actuating assembly for opening the valve when fluid under pressure is supplied to the interior of the piston to permit the flow of fluid to the space between the piston and the cylinder. We provide our assembly with means for exhausting the fluid from the space between the piston and cylinder while at the same time closing the valve which provides communication between the space within the piston and the space between the piston and cylinder to retain a reservoir of fluid under pressure within the piston so that the cushion may rapidly be returned to operation when desired. In our assembly the movement of the cushion to operative position is controlled to prevent excessive shock while at the same time permitting a rapid buildup of pressure to operating pressure after the cushion has moved to its operative position.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIGURE 1 is a sectional view through a power press provided with our improved self-contained die cushion. FIGURE 2 is a sectional view of our improved selfcontained die cushion.

FIGURE 3 is a sectional view of an alternate form of our improved self-contained die cushion.

Referring now to FIGURE 1 of the drawings, one form of press with which our improved self-contained die cushion may be used has a frame indicated generally by the reference character 10 carrying an inner slide 12 mounted for reciprocating movement with respect to the frame 10 with any suitable means such as by gibs (not shown). A gear 14 carried by the press drive shaft 16 for rotation therewith is adapted to be driven in the course of the operation of the press from a flywheel (not shown) through the medium of a clutch (not shown) in a manner known to the art. An eccentric 18 carried by the shaft 16 for rotation therewith carries a bushing 20 which supports a pitrnan 22. A bushing 28 pivotally connects the pitman 22 to a stub shaft 24 forming part of the inner slide adjusting mechanism, indicated generally by the reference character 26. The mechanism 26 is of any suitable type known to the art which is adapted to be actuated to adjust the position of the inner slide 12 with reference to the press bed to be described hereinafter. From the structure just pointed out, it will be apparent that when eccentric 18 rotates, the slide 12 reciprocates on the press frame 10.

The inner slide 12 of the press with which our im proved self-contained die cushion is used carries for move ment therewith an upper die 30 adapted to mate with a lower die 32 secured to a bolster plate 34. The upper die 30 and the lower die 32 may be secured respectively to the press slide 12 and to the plate 34 by any suitable means such for example as by bolts or clamps (not shown).

In operation of the press shown in FIGURE 1, as is known in the art, when shaft 16 is driven, the inner slide 12 descends to cause the die 30 to coact with the die 32 to form a blank 36 into the desired shape. In the course of this operation, the slide acts against knockout pins 38 carried in recesses 40 in the lower die 32.

A carrier ring 42 to which the bolster plate 34 is secured by any suitable means such as by bolts (not shown) is secured to the press bed 46 by means of clamps (not shown). Ring 42 receives a pressure plate 50 adapted to act on pins 48 carried by the bolster plate 34 to actuate the knockout pins 38 in the lower die 32. The pressure plate 50 is actuated by the cylinder 52 of our improved self-contained die cushion assembly indicated generally by the reference character 54.

Referring now to FIGURE 2 of the drawings, the cylinder 52 of the assembly 54 is slidably carried by the piston 56. We employ bolts 58 to secure plate 60 to the base 62 of the piston 56. Bolts 64 secure the plate 60 to a stationary support 66. In this manner we mount the die cushion assembly 54 at the location at which it is to be installed.

A packing 68 carried by the piston 56 is adapted to seal the space, indicated generally by the reference character 70, between the piston and cylinder. From the structure thus far described, it will be apparent that when fluid such as air under pressure is admitted to the space 70, cylinder 52 moves upwardly with respect to the piston 56 as viewed in the drawings. The limit of this relative movement is determined by the engagement of a stop ring 72 carried by the cylinder 52 with shoulder 74 carried by the piston 56.

We employ any suitable means such for example as bolts 76 to secure a top plate 78 to the piston 56. Bolts 80. secure an annular member 82 forming a valve seat 84 in a suitable opening 86 in the plate '78. Our improved self-contained die cushion includes a valve 88 positioned on a rod 90 by means of a nut 92 which holds the valve 88 in engagement with an annular shoulder 94 on the rod 90. An extension 96 of the rod 90 rides in a guide 98 to guide the rod 90 in its movement to be described hereinafter.

A sleeve 100 secured in a supporting member 102 by any suitable means such as by welding or the like surrounds the rod 90. The spring 104 bears between the upper end of the sleeve 100 as viewed in FIGURE 2 and the valve 88 normally to urge the valve 88 into engagement with the seat 84 to prevent communication between the space indicated generally by the reference character 106 within the piston 56 and the space 70.

Rod 90 extends downwardly as viewed in FIGURE 2 through the member 102 and into an actuating cylinder 108. A nut 110 screwed onto the reduced lower end portion of the rod 90 holds a piston 112 in engagement with a. shoulder 114 on the rod to secure the piston 112 to the rod for movement therewith.

We employ bolts 116 to hold the member 102 in position on the base 62 of the piston 56. A plate 118 secured to the member 102 by bolts 120 and a plate 122 secured to the top of the cylinder 108 by bolts 124 retain respective packings 126 and 128 around the rod 90 respectively to prevent the escape of fluid from the space 106 and to prevent the escape of fluid from the space within cylinder 108 over piston 112. A packing 130 carried by the piston 112 prevents the passage of fluid around the piston to the space below the piston from whence it could escape to the atmosphere. It is to be noted that, for a reason which will be pointed out hereinafter, the diameter of the piston 112 is greater than the diameter of the valve seat 84. Respective lubrication lines 132 and 134 conduct oil to the points of the cushion piston and cylinder assembly to be lubricated.

We connect a pipe or tube 136 leading from a suitable source (not shown) of fluid such as air under pressure to an opening 138 in the base 62 of the piston 56 to supply fluid under pressure to the space 106. We also connect the pipe 136 to one inlet port 140 of a valve housing 142 having a second port 144 and a third port 146 connected to exhaust pipe 148. The valve 150 is formed with a passage 152 adapted to connect two of the ports 140, 144 and 146. Valve 150 is adapted to be actuated in any suitable manner known to the art to move valve to a first position at which the passage 152 connects a port 140 to the port 144 and to a second position at which passage 152 connects port 144 to exhaust port 146.

A pipe or tube 154 connects port 144 to an opening 156 in the wall of housing 108.

Our improved self-contained die cushion assembly is provided with a pipe or conduit 158 leading from the space 70 above the plate 78 to an opening 160 formed in the base 62. We connect a two-way valve 162 of any suitable type known to the art between a pipe 164 connected to the opening 160 and an exhaust pipe 166. Valve 160 is adapted to be actuated from a normally closed position at which it prevents passage of fluid from pipe 164 to 166 to an open position at which it provides communication between pipes 164 and 166.

Referring now to FIGURE 3, we have shown an alternate form of our improved self-contained die cushion in which like parts to those shown in FIGURES l and 2 are indicated by the same reference characters. In this form of our invention We secure an annular member 168 in the opening 86 in the top 170 of the piston 56. Member 168 provides a valve seat 172 around the lower periphery of the valve opening 174 formed by the member. The valve 176 in this form of our invention is carried by a rod 178. We form valve 176 with a seat engaging surface 180 and with a portion 182 having a diameter which is slightly less than that of theopening 174. Assuming that the surface 180 of the valve 176 is in engagement with seat 172 and that the valve is operated in a manner to be described hereinafter, as the valve begins to move away from the seat a restricted passage is provided between surface 182 and the opening 174 to restrict the flow of fluid from the space within piston 56 to the space 70 to prevent the cushion from being moved too rapidly to its operative. position which goud result in undue shock when ring 72 engages shoul- Rather than providing an independent cylinder 108 in this form of our invention, we secure a plate 184 over the bottom of an opening 186 in the base 62 of the piston 56 to cause the opening 186 to form the valve operating cylinder. A piston 188 disposed within cylinder 186 is secured to rod 178 by any suitable means as by threading the lower end of the rod into the piston. A spring 190 acting between plate 184 and rod 17 8 normally tends to move the rod upwardly as viewed in FIGURE 3. In this form of our invention we provide an exhaust passage 192 in the wall of the piston 56 thus avoiding the necessity of using a separate pipe such as the pipe 158 shown in FIGURE 2 of the drawings.

In the form of our invention shown in FIGURE 3, fluid under pressure from the supply pipe 136 passes through the opening 138 to the space Within the piston 56. It will be appreciated that in this form of our invention owing to the fact that the upper end of the cylinder 186 is open, fluid under pressure supplied to the inside of the piston 56 acts on the piston 188 in a direction to move rod 178 downwardly against the action of spring 190 to move valve 176 away from seat 172.

A pipe 194 connects the supply pipe 136 to one inlet port 196 of a valve 198 adapted to be actuated by a linkage 200 indicated schematically by a broken line in FIG- URE 3 alternately to connect port 196 to a port 202 and to connect port 202 to an exhaust port 204. A valve 206 which permits free flow of fluid in the direction of the arrow B in FIGURE 3 while throttling the flow of fluid in the direction of the arrow A in FIGURE 3 connects port 202 to an opening 288 in plate 184 leading to cylinder 186 under piston 188. When it is desired to close valve 176, valve 198 is actuated in any suitable manner to connect port 196 to port 202 to supply fluid under pressure to cylinder 186. When this occurs, the pressure on both sides of piston 188 is the same and spring 190 is permitted 'to move valve 176 into engagement with its seat. When valve 176 is to be opened, valve 198 is actuated to connect port 202 to port 204 to permit the fluid under pressure below piston 188 to exhaust. The throttle valve 206 in this condition of the parts restricts the flow of fluid out of the cylinder 186 to slow the opening of valve 176 to' prevent too rapid movement of cylinder 52 to its operative position.

In the form of our invention shown in FIGURE 3 we connect pipe 164 to one inlet port 210 of a valve 212 adapted to be actuated alternately to connect port 210 to a port 214 or to a port 216 connected to an exhaust pipe 218. When it is desired to lower the cushion, valve 212 is actuated by a linkage 220 operated in any suitable manner to connect ports 210 and 218 to permit the air under pressure to be exhausted from the space 70. When the cushion is to be returned to operative position, valve 212 is actuated to connect port 210 to a port 214 which is connected to supply line 136 by a pipe 222 of reduced diameter to supply fluid under reduced pressure to the space 70 as the valve 76 opens to assist in moving the cushion to its operative position before the full pressure of the reservoir within piston 56 is applied to the space 70. This arrangement cooperates with the other features of this form of our invention in preventing too rapid a movement of cylinder 52 to its operative position while at the same time permitting a rapid buildup to operating pressure of the fluid within the space 70 after the cushion hasmoved to its operative position. From the structure just described, it will be appreciated that when the valve 17 6 is open, valve 212 should not be in a position at which port 210 is connected to port 212. We have schematically indicated a linkage 224 for ensuring that such operation does not take place.

In operation of our improved self-contained die cushion assembly when the cushion cylinder 52 is to be moved to its operative position at which it urges the knockout pins 38 to positions at which they extend above the upper surface of the lower die 32 valve 162 is closed and valve 150 is moved to a position at which it connects ports 140 and 144. In this position of the parts fluid under pressure is supplied to the space 106 and to the space within cylinder 108 over the piston 112. The fluid under pressure acting on the top of piston 112 moves rod 90 downwardly as viewed in FIGURE 2 against the action of spring 104 to move the valve 88 away from the seat 84. When this occurs, fluid under pressure is permitted to pass from the space 106 within piston 56 to the space 70 between the piston and the cylinder. This fluid under pressure causes the cylinder 52 to move upwardly as viewed in the drawings to its operative position, the limit of which is determined by the engagement of ring 72 with shoulder 74. With the cushion cylinder 52 in its operative position as the press operates shaft 16 rotates to move slide 12 downwardly to cause die 30 to engage the blank 36 and to cooperate with the lower die 32 to form the blank to the desired shape. When this happens, pins 38 are moved into the die 32 and the cushion cylinder 52 is moved downwardly by the force of the inner slide which is transmitted through pins 48 and pressure plate 50 to the cylinder. When the slide 12 returns to its top dead center position the fluid under pressure acting on the cushion cylinder urges the cylinder to move upwardly to cause pins 48 to drive knockout pins 38 to positions at which they extend above the surface of the lower die 32 to knock the formed blank out of the die.

When for any reason it is desired to lower the cushion cylinder 52 to its inoperative position, valve 150 is moved to a position at which it connects port 144 to port 146 to exhaust the air from the space within cylinder 108 over the piston 112. When this has been done, spring 104 urges the valve 88 into engagement with seat 84 to prevent communication between spaces 106 and 70. Valve 162 is then opened to exhaust the fluid under pressure from the space 70 to permit cylinder 52 to move to its inoperative position. It will be appreciated that with this disposition of parts, fluid under pressure is acting on valve 88 firmly to hold it in engagement with seat 84. In this manner, the reservoir of fluid under pressure in space 106 is preserved.

When the cushion is to be placed in operation, valve 162 is closed and valve is moved to a position at which it connects ports 140 and 144 to supply fluid under pressure to the space within cylinder 108 over piston 112. Since the diameter of piston 112 is greater than that of valve 88 the fluid under pressure acting on the piston moves rod 90 downwardly to move valve 88 away from seat 84 to permit fluid under pressure to flow from the space 106 to the space 70. This fluid under pressure again raises cylinder 52 to its operative position.

In operation of the form of our invention shown in FIG- URE 3 assuming the cushion is in its operative position so that valve 176 is closed and valve 212 is in the position at which it connects ports 210 and 214 valve 198 is actuated to connect ports 202 and 196 to supply fluid under pressure to the underside of piston 188 to permit spring 190 to close valve 176 on its seat 172. After valve 176 closes, valve 212 is actuated to connect ports 210 and 216 to exhaust fluid under pressure from the space 70 through the passage 192 and through valve 212.

When it is desired to return the cushion to its operative position valve 212 is actuated to connect ports 2 10 and 214 and valve 198 is actuated to connect ports 202 and 204. In this condition of the parts valve 176 moves away from seat 172 slowly owing to the throttling eflect of valve 206 and the space between the valve portion 182 and the surface 174 restricts the flow of fluid from within the piston 56 to the space 70. At the same time fluid under reduced pressure is supplied to the space 70 from pipe 222 through valve 212. In this manner the cushion moves to its operative position in such a way as prevents excessive shock forces from being applied to the parts. When the cushion arrives at its operative position valve 176 opens fully and the pressure within space 70 rapidly builds up to operating pressure.

It will be appreciated that owing to the fact that the reservoir of fluid under pressure within the space 106 is preserved while the cylinder 52 is being lowered to its inoperative position cylinder 52 may be returned to its operating pressure inoperative position rapidly without the necessity of employing large diameter pipes leading to external tanks.

It will be seen that we have accomplished the objects of our invention. We have provided a self-contained die cushion which permits the fluid between the cushion piston and the cylinder to be rapidly exhausted while at the same time enabling the cushion to be returned rapidly to operating pressure at its operative position. We accomplish this result without requiring large diameter pipes and valves for connecting the cushion to a tank external to the press bed. Our self-contained die cushion can be rapidly stroked and there is little danger of excessive buildup in our cushion.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim 1. A self-contained die cushion assembly including in combination a hollow piston, a cylinder, said piston and cylinder being telescoped for relative movement and to enclose a space therebetween, means for maintaining a reservoir of fluid under pressure within said piston, a normally closed valve adapted to be actuated to connect said reservoir to the space between said piston and cylinder and means for actuating said valve to provide communication between fluid under pressure in said reservoir and the space enclosed by said piston and cylinder.

2. A self-contained die cushion assembly including in combination a hollow piston, a cylinder, said piston and cylinder being telescoped for relative movement and to enclose a space therebetween, means for maintaining a reservoir of fluid under pressure within said piston, a normally closed valve, means for opening said valve to provide communication between said reservoir and the space between said piston and cylinder, a normally closed exhaust valve, and means for opening said exhaust valve to provide communication between the space between said piston and said cylinder and the atmosphere.

3. A self-contained die cushion assembly including in combination a hollow piston, a cylinder telescopically mounted on said piston for relative movement and to enclose a space therebetween, means for supplying fluid under pressure to the interior of said piston, a normally closed valve, means for opening said valve to provide communication between the interior of the piston and the space between the piston and the cylinder, an auxiliary cylinder, an auxiliary piston, means mounting said auxiliary cylinder and piston for relative movement in cooperative relationship, means adapted to be actuated to supply fluid under pressure to the auxiliary cylinder for actuating said opening means.

4. A self-contained die cushion assembly including in combination a hollow piston, a cylinder telescopically mounted on said piston for relative movement and to enclose a space therebetween, means for supplying fluid under pressure to the interior of said piston, an auxiliary cylinder, an auxiliary piston, means mounting said auxiliary cylinder and piston for relative movement in cooperative relationship, said piston formed with an opening providing communication between the interior of the piston and said space, a valve for controlling said opening, means responsive to said auxiliary piston for opening said valve, means normally urging said valve to closed position, means adapted to be actuated to supply fluid under pressure to the auxiliary cylinder to move said auxiliary piston to open said valve against the action of said urging means and an exhaust valve adapted to be actuated to exhaust fluid under pressure from the space between said cylinder and said piston.

5. A self-contained die cushion assembly including in combination a hollow piston, a cylinder telescopically mounted on said piston for relative movement and to enclose a space therebetween, means for supplying fluid under pressure to the interior of said piston, an auxiliary cylinder, an auxiliary piston, means mounting said auxiliary piston and cylinder for relative movement in cooperative relationship, said piston formed with an opening providing communication between the interior of the piston and said space, a valve for controlling said opening, means responsive to said auxiliary piston for opening said valve, means normally urging said valve to closed position, means adapted to be actuated to supply fluid under pressure to the auxiliary cylinder to move the auxiliary piston to open said valve against the action of said urging means and an exhaust valve adapted to be actuated to exhaust fluid under pressure from the space between said cylinder and said piston, said auxiliary piston having a diameter which is greater than that of said opening.

6. A self-contained die cushion assembly including in combination a hollow piston, a cylinder, said piston and cylinder being telescoped for relative movement and to enclose a space therebetween, means for maintaining a reservoir of fluid under pressure within said piston, a normally closed valve adapted to be actuated to connect said reservoir to the space between said piston and cylinder, said valve being constructed to provide a restricted passage for the flow of fluid during the initial opening movement thereof and a relatively large passage when said valve is open and means for actuating said valve to provide communication between fluid under pressure in said reservoir and the space enclosed by said piston and cylinder.

7. A self-contained die cushion assembly including in combination a hollow piston, a cylinder, said piston and cylinder being telescoped for relative movement and to enclose a space therebetween, means for maintaining a reservoir of fluid under pressure within said piston, a normally closed valve adapted to be actuated to connect said reservoir to the space between said piston and cylinder, said valve being constructed to provide a restricted passage for the flow of fluid during the initial opening movement thereof and a relatively large passage for the flow of fluid when fully open, means for actuating said valve to provide communication between fluid under pressure in said reservoir and the space enclosed by said piston and cylinder and means for retarding the actuation of said valve.

8. A self-contained die cushion assembly including in combination a hollow piston, a cylinder, said piston and cylinder being telescoped for relative movement and to enclose a space therebetween, means for maintaining a reservoir of fluid under pressure within said piston, 21 normally closed valve adapted to be actuated to connect said reservoir to the space between said piston and cylinder, said valve being constructed to provide a restricted passage for the flow of fluid during the initial opening movement thereof and a relatively large passage for the flow of fluid when fully open, means for actuating said valve to provide communication between fluid under pressure in said reservoir and the space enclosed by said piston and cylinder and means for supplying fluid under reduced pressure to the space between said piston and cylinder when said valve is actuated.

References Cited in the file of this patent UNITED STATES PATENTS 1,042,094 Demmler Oct. 22, 1912 2,337,573 Schultz Dec. 28, 1943 FOREIGN PATENTS 727,976 Great Britain Apr. 13, 1955 

1. A SELF-CONTAINED DIE CUSHION ASSEMBLY INCLUDING IN COMBINATION A HOLLOW PISTON, A CYLINDER, SAID PISTON AND CYLINDER BEING TELESCOPED FOR RELATIVE MOVEMENT AND TO ENCLOSE A SPACE THEREBETWEEN, MEANS FOR MAINTAINING A RESERVOIR OF FLUID UNDER PRESSURE WITHIN SAID PISTON, A NORMALLY CLOSED VALVE ADAPTED TO BE ACTUATED TO CONNECT SAID RESERVOIR TO THE SPACE BETWEEN SAID PISTON AND CYLINDER AND MEANS FOR ACTUATING SAID VALVE TO PROVIDE COMMUNICATION BETWEEN FLUID UNDER PRESSURE IN SAID RESERVOIR AND THE SPACE ENCLOSED BY SAID PISTON AND CYLINDER. 